Viper? I Hardly Knew Her!

As other alien invaders on earth are being exposed, the platoon becomes concerned for their own security. Soon an intruder is discovered, but she turns out to be Natsumi's new classmate and the friend of the missing Zeroro. Disappointed and feeling abandoned all those months, the new Dororo breaks off relations with the platoon. In the house, Keroro reflects back on how he, Giroro and Zeroro were childhood friends and included some of the trauma he caused.
In the meantime, Dororo and Koyuki have been kidnapped by Viper. The platoon attempts a rescue operation, but is quickly defeated by Viper (who is much stronger than the incomplete platoon). A remorseful Keroro wholeheartedly apologizes to Dororo for breaking his prized music box and awakens him. The now complete platoon, using an energy ball defeats Viper. However, the shock of knowing that Keroro broke the music box greatly upsets Dororo and causes him to reconsider joining the platoon.